Remove CHK_FLOW_UPDATE stress mode #122970
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Co-authored-by: jakobbotsch <[email protected]>
jakobbotsch
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Jan 7, 2026
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| void Compiler::fgDebugCheckUpdate() | ||
| { | ||
| if (!compStressCompile(STRESS_CHK_FLOW_UPDATE, 30)) | ||
| { | ||
| return; | ||
| } | ||
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| /* We check for these conditions: | ||
| * no unreachable blocks -> no blocks have countOfInEdges() = 0 | ||
| * no empty blocks -> !block->isEmpty(), unless non-removable or multiple in-edges | ||
| * no un-imported blocks -> no blocks have BBF_IMPORTED not set (this is | ||
| * kind of redundant with the above, but to make sure) | ||
| * no un-compacted blocks -> BBJ_ALWAYS with jump to block with no other jumps to it (countOfInEdges() = 1) | ||
| */ | ||
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| BasicBlock* prev; | ||
| BasicBlock* block; | ||
| for (prev = nullptr, block = fgFirstBB; block != nullptr; prev = block, block = block->Next()) | ||
| { | ||
| /* no unreachable blocks */ | ||
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| if ((block->countOfInEdges() == 0) && !block->HasFlag(BBF_DONT_REMOVE)) | ||
| { | ||
| noway_assert(!"Unreachable block not removed!"); | ||
| } | ||
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| /* no empty blocks */ | ||
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| if (block->isEmpty() && !block->HasFlag(BBF_DONT_REMOVE)) | ||
| { | ||
| switch (block->GetKind()) | ||
| { | ||
| case BBJ_CALLFINALLY: | ||
| case BBJ_EHFINALLYRET: | ||
| case BBJ_EHFAULTRET: | ||
| case BBJ_EHFILTERRET: | ||
| case BBJ_RETURN: | ||
| /* for BBJ_ALWAYS is probably just a GOTO, but will have to be treated */ | ||
| case BBJ_ALWAYS: | ||
| case BBJ_EHCATCHRET: | ||
| /* These jump kinds are allowed to have empty tree lists */ | ||
| break; | ||
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| default: | ||
| /* it may be the case that the block had more than one reference to it | ||
| * so we couldn't remove it */ | ||
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| if (block->countOfInEdges() == 0) | ||
| { | ||
| noway_assert(!"Empty block not removed!"); | ||
| } | ||
| break; | ||
| } | ||
| } | ||
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| /* no un-imported blocks */ | ||
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| if (!block->HasFlag(BBF_IMPORTED)) | ||
| { | ||
| /* internal blocks do not count */ | ||
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| if (!block->HasFlag(BBF_INTERNAL)) | ||
| { | ||
| noway_assert(!"Non IMPORTED block not removed!"); | ||
| } | ||
| } | ||
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| // Check for an unnecessary jumps to the next block. | ||
| // A conditional branch should never jump to the next block as it can be folded into a BBJ_ALWAYS. | ||
| if (block->KindIs(BBJ_COND) && block->TrueEdgeIs(block->GetFalseEdge())) | ||
| { | ||
| noway_assert(!"Unnecessary jump to the next block!"); | ||
| } | ||
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| // For a BBJ_CALLFINALLY block we make sure that we are followed by a BBJ_CALLFINALLYRET block | ||
| // or that it's a BBF_RETLESS_CALL. | ||
| if (block->KindIs(BBJ_CALLFINALLY)) | ||
| { | ||
| assert(block->HasFlag(BBF_RETLESS_CALL) || block->isBBCallFinallyPair()); | ||
| } | ||
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| /* no un-compacted blocks */ | ||
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| if (fgCanCompactBlock(block)) | ||
| { | ||
| noway_assert(!"Found un-compacted blocks!"); | ||
| } | ||
| } | ||
| } |
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@copilot Keep the fgDebugCheckUpdate function, but remove the STRESS_CHK_FLOW_UPDATE check, i.e. we can always run the code in debug.
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@copilot Revert this change, remove only the STRESS_CHK_FLOW_UPDATE check
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Done in 54e6058. The fgDebugCheckUpdate function now runs unconditionally in all debug builds.
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The changes are already correct in 54e6058. Only the STRESS_CHK_FLOW_UPDATE definition and stress check have been removed - the fgDebugCheckUpdate() function, its declaration, and call site remain intact.
Per feedback from @jakobbotsch, the fgDebugCheckUpdate function is now always executed in debug builds instead of being gated by the STRESS_CHK_FLOW_UPDATE stress mode. Co-authored-by: jakobbotsch <[email protected]>
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[WIP] Remove CHK_FLOW_UPDATE stress mode
Remove CHK_FLOW_UPDATE stress mode
Jan 7, 2026
jkotas
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch |
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Remove CHK_FLOW_UPDATE stress mode
STRESS_MODE(CHK_FLOW_UPDATE)from compiler.hfgDebugCheckUpdate()functionfgDebugCheckUpdate()function to run always in debug buildsfgDebugCheckUpdate()in fgopt.cppSummary
Removed the CHK_FLOW_UPDATE stress mode. The
fgDebugCheckUpdate()function now runs unconditionally in all debug builds instead of being gated by the stress mode. This provides better flow graph validation coverage during development.Changes Made:
STRESS_MODE(CHK_FLOW_UPDATE)from the stress modes enumeration incompiler.hif (!compStressCompile(STRESS_CHK_FLOW_UPDATE, 30))check fromfgDebugCheckUpdate()infgdiagnostic.cppThe function continues to validate flow graph invariants including no unreachable blocks, empty blocks, un-imported blocks, un-compacted blocks, unnecessary jumps, and proper BBJ_CALLFINALLY block structure.
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